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Y. Koutalos, C. Chen, D. A. Thompson; Reduction of All-Trans Retinal in the Outer and Inner Segments of Single Isolated Rod Photoreceptors of Rdh12-Deficient Mice. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4812.
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© ARVO (1962-2015); The Authors (2016-present)
To examine the reduction of all-trans retinal to retinol in living mouse rod photoreceptors of mice lacking retinol dehydrogenase 12 (RDH12). The toxicity of all-trans retinal is thought to play a key role in several diseases of the retina. Loss-of-function mutations of RDH12 cause severe visual handicap and are associated with Leber Congenital Amaurosis.
Experiments were carried out with single isolated rod photoreceptors from wild-type and Rdh12-/- mice. Animals were 2-5 months old. The reduction of all-trans retinal was measured from the fluorescence of the generated retinol (Ex: 360 nm; Em: >420 nm) in the inner and outer segments of the cells. All-trans retinal was generated endogenously within the outer segment by bleaching rhodopsin, or was supplied exogenously with bovine serum albumin as carrier. Experiments were carried out at 37 0C.
There was no difference between wild-type and Rdh12-/- cells in the reduction of all-trans retinal that was generated endogenously by a single full bleach of the photoreceptor cells. There was also no difference in the ability of the outer segments of the two types of mice to reduce exogenously supplied all-trans retinal. However, the inner segments of Rdh12-/- cells reduced 5 µM exogenous all-trans retinal at a significantly slower rate.
The decreased capacity of the photoreceptors from Rdh12-deficient mice to reduce exogenously supplied all-trans retinal is consistent with the localization of RDH12 in the photoreceptor inner segment. The absence of a discernible effect of Rdh12-deficiency on the clearance of all-trans retinal resulting from a full bleach is consistent with the view that RDH12 is not essential for visual cycle function. These findings suggest that the physiological role of RDH12 is broader than just protecting the photoreceptor inner segment against all-trans retinal generated by acute light exposures, and could involve protecting against a wide spectrum of aldehydes or all-trans retinal generated during continuous light exposures.Support: NIH/NEI grant EY14850 (YK), Foundation Fighting Blindness and Research to Prevent Blindness, Inc.
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